Development and Evaluation of a Test Strip for Estimating the pH, Chloride and Sulfate Levels in Engine Coolants

A three-pad dip-and-read test strip has been developed for determining whether the pH, chloride and sulfate levels in engine coolant samples lie within or exceed the recommended ranges. The preferred ranges are 7.5 to 11.0 for pH, below 200 ppm for chloride ion, and below 1500 ppm for sulfate ion. Conditions outside of these limits can lead to corrosion of engine cooling system metal surfaces. A quick and convenient test can determine whether the coolant is suitable for continuing use or should be drained from the system. Extensive performance and stability evaluations of the test pads have been carried out, to ensure that the test strip results agree with reference method results and that test strips are stable under normal storage and use conditions. The test strips were evaluated with different glycol levels, with both ethylene and propylene glycol samples, and under different lighting sources. Test strips were evaluated after storing for varying periods of time at various elevated temperatures and under humidity conditions, to establish whether the strips would retain adequate reactivity with normal use. The results of these evaluations indicate that the strips are adequately accurate and stable for monitoring the condition of engine coolants.